Poor drainage help.

[Solefate]

Hey guys. I bought an older house that has no main vent going out through the roof. Whenever the washing machine drains on medium or large, air backs up into the toilet. I recently replumbed all the washer hookups and added a trap and an AAV. However it did not fix the problem. Do I need to add another AAV somewhere, or a main vent line? If so, where on the line?

/e excuse my awesome drawing skills.

 

[frodo]

the drain from the washer must be a minimum of 5' aaway from the toilet
before it ties into the main line. because of suds relief.

If it is closer than 5' the suds and water will bubble up into the tub/shower and or toilet

that is what it sounds like your problem is

 

[Solefate]

Can I do something like this? Or will adding those 90s hurt me?